Continuously variable dimmer switch



Dec. 6, 1966 V s. SLATER Re. 26,119

GONTINUOUSLY VARIABLE DIMMER SWITCH Original Filed June I0, 1960 5Sheets-Sheet 1 IN VEN TOR. 5/204 51 A 752 aYMguZ/f Dec. 6, 1966 s.SLATER Re. 26,119

CONTINUOUSLY VARIABLE DIMMER SWITCH Original Filed June 10. 1960 5Sheets-Sheet \02 :0: M FIG. 8

LOAD

INVENTOR SAUL I. SLATER ATTORNEYS United States Patent Re. 26,119Reissued Dec. 6, 1966 [ice CONTINUOUSLY VARIABLE DIMMER SWITCH Saul I.Slater, Glen Cove, N.Y., assignor to Slater Electric Inc., Glen Cove,N.Y., a corporation of New York Original No. 3,103,618, dated Sept. 10,1963, Ser. No.

35,298, June 10, 1960. Application for reissue Nov.

16, 1965, Ser. No. 516,821

7 Claims. (Cl. 323-22) Matter enclosed in heavy brackets appears in theoriginal patent but forms no part of this reissue specification; matterprinted in italics indicates the additions made by reissue.

This invention relates to power control devices, and more particularlyto a continuously variable dimmer switch for applications such as lampdimming and the like.

The present invention includes an improvement on and may be considered acontinuation-in-part of my copending patent application Serial No. 3,144for Continuously Variable Dimmer Switch," filed January 18, 1960, nowabandoned, which had the same disclosure as my application Serial No.250,458 for Continuously Variable Dimmer Switch, filed January 4, 1963.

The aforementioned copending patent application discloses a continuouslyvariable dimmer switch having, in addition to full-on and full-offpositions, a range of positions in which the power supplied to anelectrical load device is continuously variable. The dimmer switch is atwo terminal switch device which may be directly sub stituted for astandard, single-pole, single-throw switch in conventional, domesticelectric outlet boxes and the like. Unlike many of the prior artdevices, utilized for lamp dimming and similar applications, such asvariable transformer or auto-transformers, for example, the aforesaiddimmer switch need only be connected into one side of the alternatingcurrent supply line to the load. Furthermore, it is of smaller size,lower cost and is more easily installed. The dimmer switch employs asilicon controlled rectifier which is coupled between the two switchterminals in series with the load device. A time delay circuit, such asa variable phase shift circuit, for example, is also coupled between thetwo switch terminals to provide a controllable gating signal for thegate electrode of the rectifier. By controlling the phase of the gatingsignal, it is possible to control the portion of an applied alternatingcurrent cycle over which the rectifier conducts, to thereby control thepower supplied to the load. The variable phase shift circuit maycomprise serially-coupled capacitor and variable resistance elementswhich are connected in parallel circuit with the rectifier across theswitch terminals. The gate electrode of the controlled rectifier iscoupled to the circuit junction of the capacitance and the variableresistance by means of a limiting resistor and a diode, so that avariation in the resistance of the circuit caused by adjustment of thevariable resistance element varies the phase of the voltage applied tothe gate element with respect to the phase of the switch terminalvoltage, to thereby vary the power supplied to the load device in amanner somewhat similar to a grid-controlled thyratron. Additionally,the device disclosed in the aforesaid copending patent ap' plication maysupply full power to the load device or may completely shut off thepower to the load device by means of one or more switches which may beconveniently actuated by the same control means used to control thevariable resistance in the phase shift circuit.

While the above-described continuously variable dimmer switch may bephysically constructed to occupy an extremely small space, such as wouldcomfortably fit into a standard electric outlet box, for example, it isnevertheless desirable to provide such a device which occupies a stillsmaller space and yet which is capable of handling reasonably largeamounts of load power. For example, it is desirable that electric switchcomponents be made of a small enough physical size to enable two orthree of them to be mounted in a standard electric outlet box withoutexceeding the heat dissipation requirements iniposed by the varioussafety codes. A common method of mounting a number of switches or othercircuit devices in a standard outlet box makes use of a so-calledDespard" mounting strap which usually permits three such circuit devicesto be supported in a single box. When a number of switches are mountedin this manner, the problem of heat dissipation becomes severe, due tothe relatively small heat dissipation area available for each switch.Obviously, the silicon controlled rectifier produces a substantialamount of the heat to be dissipated. However, the variable resistance ofthe phase shift circuit also contributes to the heat output and, moreimportantly, also tends to limit the minimum physical size which theswitch device may assume.

Accordingly, it is an object of this invention to provide a powercontrol device which is capable of supplying substantial amounts ofpower to a load device over a substantial range of power values and yetwhich is capable of assuming an extremely small physical size.

It is another object of the present invention to provide a continuouslyvariable light dimming circuit which is in all cases directlysubstitutable in a circuit which previously employed the customarysingle pole-single throw switch; that is, the circuit, according to thepresent invention, may be inserted where access is available to only oneof the two lines leading to an electrical device to be controlled by thedimmer switch.

It is a further object of this invention to provide an improvedcontinuously variable dimmer switch of the type disclosed in myaforementioned copending patent application for controlling electriclamps and the like, which improved dimmer switch occupies a much smallerphysical space without diminishing its power handling capacity.

It is a still further object of this invention to provide a continuouslyvariable dimmer switch which is of such a compact size as to enable aplurality of such switches to be mounted in a single standard sizeelectric outlet box.

It will be useful to explain generally the advantages provided by thecircuits described herein compared to that of my prior copendingapplication Serial No. 3,144.

Briefly, for a given amount of load power-handling capacity, thephysical size of the continuously variable dimmer switch depends to alarge extent upon the size of the variable resistance in the phase shiftcircuit for the silicon controlled rectifier. Since, for a givenpowerhandling capacity, the size of the silicon controlled rectifier issubstantially fixed, and since the gating current required to controlthe rectifier is determined by the electrical characteristic of therectifier, the required reduction in physical size is preferablyobtained in the phase shift circuit. The present invention proposed toaccomplish this by the inclusion of a simple, commercially availablediode of small size serially coupled in the phase shift circuit with thecapacitance and variable resistance. When such a diode is included inthe phase shift circuit, the output of the diode which energizes thecircuit contains a direct current component and an alternating currentor ripple" component. Accordingly. it is then possible to utilize avariable resistance of a much smaller size to provide substantially thesame phase shift operathe diode in series with the phase shift circuitmakes it possible to omit the diode previously employed with thelimiting resistor in the input to the gate electrode of the siliconcontrolled rectifier without danger of damaging the rectifier. Theimproved continuously variable dimmer switch of the invention alsoincludes means for dissipating the heat produced by the siliconcontrolled rectifier to enable a number of the smaller sized switches tobe mounted in a single outlet box of standard size without exceeding asafe operating temperature.

In the drawings:

FIG. 1 is a schematic circuit diagram of the improved continuouslyvariable dimmer switch of the present invention'.

FIG. 2 is a front elevational view of a suitable switchplate and housingfor the dimmer switch of FIG. l;

FIG. 3 is a side elevational view of the switch plate and housing ofFIG. 2 with a portion of the housing broken away to reveal details ofconstruction;

FIG. 4 is a side elevational view of a variable resistance and switchassembly which could be employed in the device of FIG. 1',

FIG. 5 is a sectional view taken along the line 5--5 of FIG. 4;

FIG. 6 is a sectional view taken along the line 6-6 of FIG. 5;

FIG. 7 is a front elevational view showing three of the improvedcontinuously variable dimmer switches of the present invention mountedin a standard size electric outlet box;

FIG. 8 is a schematic circuit diagram of an alternative form of variabledimmer switch according to the present invention; and

FIG. 9 is a schematic circuit diagram of a further alternative form ofcontinuously variable dimmer switch according to the present invention.

Referring now to FIG. 1 of the drawings, there is shown a continuouslyvariable dimmer switch 10 constructed in accordance with the teachingsof the present invention and having two switch terminals 11 and 12. Theswitch 10 is connected by the terminals 11 and 12 in series circuit witha load device 13 and the terminals 14 and 15 of a source of alternatingvoltage, which may, for example, be the conventional 1l5 volt, 60 cyclehousehold power supply. In accordance with the usual wiring practice,the supply terminal 15 may be grounded, so that the switch 10 isconnected in the hot" side of the load supply line. The load 13 maycomprise one or more incandescent lamps or certain types of otherequipment, such as heaters or motors, for example. Since the dimmerswitch provides a half-wave output having a direct current component,load devices suitable only for alternating current operation may not beemployed. It will be noted that the switch 10 is a two terminal devicehaving terminals 11 and 12, so that it need be connected in only oneside of the line supplying the load 13. This is quite important since itpermits the dimmer switch of the invention to be directly substitutedfor the usual, single-pole, single-throw switch customarily employed inhousehold and other similar applications. The usual types of dimmerarrangement, such as those utilizing variable transformers orauto-transformers, for example, require that the dimmer device beconnected into both sides of the power supply line, with the result thatthese devices cannot be wired into the usual household circuits withoutexpensive alterations. The dimmer switch itself comprises a siliconcontrolled rectifier 16 having an anode electrode 17, a cathodeelectrode 18, and a gate electrode 19 and is serially connected betweenthe switch terminals 11 and 12 by a lead 20. The silicon controlledrectifier 16 is a PNPN semi-conductor device which operates in a mannersimilar to a grid-controlled thyratron. The reverse current blockingcharacteristic of the silicon controlled rectifier is generally similarto that of silicon rectifiers or to other types of rectifiers. However,the

forward current in the silicon controlled rectifier is controlled by agating signal which is applied to the gating electrode 19 to instituteor start forward conduction. Similar to the tliyratron, the siliconcontrolled rectifier continues to conduct in a forward direction onceconduction has been started, even after the gating signal has beenremoved. Unlike the thyratron, however, the gating or control signal forthe rectifier is essentially a cur rent signal rather than a voltagesignal. Usually, in order to drive the rectifier into forwardconduction, the gate electrode is biased positive with respect to thecathode electrode.

In operation, the silicon controlled rectifier 16 functions to controlthe power output to the load 13 by varying the portion of thealternating current cycle applied to terminals 11-12 over which therectifier conducts. A explained in more detail in the aforementionedcopending patent application, a time delay circuit, which may comprise aphase shift circuit, for example, is employed to control the point inthe cycle of applied line voltage at which the rectifier 16 conducts andtherefore controls the power applied to the load 13. To this end, switchterminal 11 is coupled by means of a lead 21, a diode 22, a variableresistance-switch assembly 23, a capacitor 24 and a lead 25 to theswitch terminal 12. The variable resistance-switch assembly 23 comprisesa variable resistance 26 having a movable wiper arm 27 and a pair ofswitches 28 and 29. Leads 30 and 31 serve to connect switch 28 in seriescircuit with the wiper arm 27 of the variable resistance and thecapacitor 24. The switch 29 is connected in parallel with the siliconcontrolled rectifier 16 directly across the switch terminals 11 and 12by means of leads 21, 32, 33 and 25. The wiper arm 27 of the variableresistance and the movable contacts of the switches 28 and 29 aremechanically interconnected as indicated schematically by the dottedline 34, so that these elements may be operated in a predeterminedsequence by rotation of a control knob 35, as will be more fullyexplained hereinafter. The circuit junction of capacitor 24 and variableresistance 26 is connected to the gate electrode 19 of the siliconcontrolled rectifier 16 by means of a limiting resistance 36 and a lead37. The gate electrode 19 is also connected to the cathode electrode 18of the rectifier through lead 37, an adjusting resistor 38 and leads 25and 20. Resistor 38 is employed to compensate for the variations in gatecurrent encountered during a normal production run of the siliconcontrolled rectifier. Since, in a normal production run of suchrectifiers, the gate or "trigger" current varies widely from rectifierto rectifier, the resistor 38 may be used to desensitize thoserectifiers having a very low gate current, to thereby permit the valuesof the other circuit elements to be standardized. Accordingly, resistor38 may be omitted, if desired, so that the potential at the gateelectrode 19 is essentially the same as the potential at the circuitjunction of capacitor 24 and variable resistance 26. Finally, acapacitor 39 is shunted directly across the controlled rectifier 16 andthe switch terminals 11 and 12 by means of a lead 40 to minimize anyinterference with radio or television equipment which might be producedby the operation of the switch.

In operation, capacitor 24 and variable resistance 26 form a variabletime delay or phase shift circuit in which the voltage appearing at thecircuit junction of capacitor 24 and resistance 26 is of variable phasewith respect to the phase of the voltage appearing at terminal 11 of thedimmer switch 10. When the variable resistance 26 is completely shortedout by moving the wiper arm 27 to the end of the resistance adjacentdiode 22, the phase of the voltage measured at the circuit junction ofthe capacitor and variable resistance will be substantially the same asthat measured at switch terminal 11. However, when the wiper arm 27 ofthe variable resistance 26 is moved to place some resistance into thecircuit, the phase of the voltage at the circuit junction of thecapacitor and variable resistance will lag the phase of the voltageappearing at switch terminal 11 by an amount generally proportional tothe amount of resistance provided by the variable resistance 26. Sincethe phase of the voltage at the circult junction of capacitor 24 andvariable resistance 26 determines the phase of the gating signal appliedto gate electrode 19 of the silicon controlled rectifier 16, itdetermines the point on the applied cycle of supply voltage at which therectifier begin forward conduction and therefore determines the poweroutput passed by the rectifier to the load 13. Accordingly, by actuatingcontrol knob 35 to vary resistance 26, it is possible to control thepower supplied to load 13.

Since the diode 22 is in series circuit with the variable resistance 26and the capacitor 24, the energizing source for the phase shift circuitwill supply half-wave, pulsating direct current having a direct currentcomponent and an alternating current or ripple" component of the samefrequency as the line voltage at input terminals 14 and 15. By utilizinga half-wave rectifier or diode, the power that the variable resistance26 must handle is very greatly reduced, so that it is possible to employa variable resistance of greatly reduced physical size. It will benoted, of course, that the diode 22 still permits the required phaseshift control for the controlled rectifier 16, since the capacitor 24still is charged with a delay controllable by variable resistance 26.Furthermore, it is no longer necessary to employ a diode in lead 37 [orthe gate electrode 19, as in the dimmer switch of my aforementionedcopending patent application, to assure that the gate control currentwill be of the correct polarity to prevent damage to the rectifier 16.

By suitably arranging the operating sequence of variable resistance 26and switches 28 and 29 of the variable resistance-switch assembly 23, itis possible to apply full .power or to completely shut off power to theload 13 in addition to providing a range of continuously controlledpower. This may be accomplished by causing the mechanicalinterconnection 34 to maintain both switches 28 and 29 in an openedcondition and the wiper arm 27 at the full resistance position ofvariable resistance 26 when the control knob 35 is in an off position,for example, at the extreme counterclockwise position of its range ofrotation. At this time, the only direct connection to the load 13 fromthe input terminal 14 is through the silicon controlled rectifier 16.However, the rectifier is prevented from conducting because switch 28 isopened in the phase shift circuit. As the knob 35 is rotated in aclockwise direction, switch 28 is arranged to close and switch 29remains open, so that the phase shift circuit becomes oper able tocontrol the conducting point of rectifier 16. Switch 28 can be placed atany point along the conductive path to terminal 11 and may be betweenterminal II and leads 20 and 21 as in my application Serial No. 3,144,filed January 18, 1960, now abandoned. As the knob 35 is rotated, lessand less resistance is provided in the phase shift circuit by thevariable resistance 26, so that the rectifier 16 conducts at pointscloser and closer to the start of the cycle of supply voltage,Therefore, the power supplied to load 13 gradually increases withclockwise rotation of knob 35 until the variable resistance 26 iscompletely shorted out. At this time, the mechanical interconnection 34is arranged to close switch 29 to bypass rectifier 16 and therebydirectly connect the load 13 across the input terminals 14 and 15. Thisfull-on" position, of course, applies full line voltage and power to theload. While continuous variability is not provided throughout the rangefrom off to full power in the circuit of FIG. 1, the continuouslyvariable range is particularly effective as a practical matter, when theswitch is used in conjunction with incandescent lamps. At low powers,incandescent lamps have a marked drop in efficiency for the productionof visible light, so that the variable dimmer switch readily allows thedimming of an incandescent lamp until its light output is about 2percent of its maximum value. It is believed apparent that furtherdimming would be of relatively little value in the usual householdapplication. When the dimmer switch of the invention is employed inhousehold or similar aprplications, the capacitor 39 may be utilized asshown to shunt the rectifier 16 to minimize the effects of spuriousfrequencies produced by the rectifying action on radio and televisionsets and the like.

FIG. 2 of the drawings illustrates the improved dimmer switch of theinvention mounted on a switch plate 50. The control knob 35 of thevariable resistance-switch assembly 23 is provided with a pointer 51which cooperates with an Off" position marking 52 and a Bright" positionmarking 53 on the face of the plate to provide an indication of thelight level of the lamp or lamps which the switch is controlling. Asseen in FIG. 3 of the drawings, the component parts of the dimmer switch10 may be enclosed in a box-like housing 54 of plastic or otherpreferably non-conducting material. The housing 54 is provided withprojections 55 which may be utilized to secure the switch to aninterchangeable mounting plate or other device for supporting the switchin the usual electric outlet box. The variable resistance-switchassembly 23 is arranged to be controlled by the knob 35 by means of asingle shaft 56. The silicon controlled rectifier 16 is mounted on asupport plate 57 by means of a nut 58, so that the rectifier envelopemaintains a good physical contact with the plate to enable good heatconduction to take place. The plate 57 is preferably made of copper orother material having good heat conductivity and extends along the rearand the two side walls of the housing 54 in close physical contacttherewith. By virtue of this arrangement, the heat produced by therectifier 16 is conducted along the plate 57 which forms a heat "sink"in the manner described in my copending patent application, Serial No.5,000, filed January 27, l960, for Light Dimming Switch, now Patent No.3,037,146, and is then transferred through the walls of the housing 54over a broad area to enable it to be readily dissipated. If desired, anadditional heat sink in the form of U-shaped plate 59 may be employedaround the outside walls of the housing 54, as illustrated, to furtheraid in dissipating the heat generated by the rectifier 16. Furthermore,the additional heat sink 59 may be soldered to the mounting strap forthe switch to provide a still further increase in heat dissipating areafor the switch. The switch terminals 11 and 12 may be brought outthrough openings (not shown) formed in the top and bottom walls ofhousing 54 to facilitate the making of connections to existing housewiring. The remainder of the components for the dimmer switch, includingdiode 22, capacitors 24 and 39, and resistors 36 and 38 may beconveniently positioned in any space available in the housing 54 bysupporting them directly on the wire leads to the components or byseating them in openings formed in the housing itself.

The structural details of a suitable mechanical arrangement for thevariable resistanceswitoh assembly 23 of the dimmer switch are shown inFIGS. 4-6 of the drawings. As seen in FIG. 4, the assembly comprises avariable resistance portion 60, which may be a. simple vari ableresistor of the type utilized in radio and television receiving sets,for example, and a switch portion 61 which is directly mounted on thehousing of the variable resistance portion 60. The variable resistor isactuated by rotation of control shaft 56 which is seated in a threadedsleeve 62 having a mounting nut 63 thereon. When the assembly is placedin the housing 54 of the switch, it may be secured to the front portionof the housing by means of the threaded sleeve 62 and the mounting nut63. The terminals for the potentiometer 60 are indicated generally at 64and the terminals for the switch portion 61 are indicated generally at65. As seen in FIG. 5 of the drawings, the switch portion 61 is asubstantially separate unit which is actuated by an extended, flattenedportion 66 of the control shaft 56. The shaft portion 66 has mountedthereon a pair of earns 67 and 68 which respectively control theswitches 29 and 28. (am 67 is arranged to actuate switch 29 by means ofa cam-follower projection 69 formed on the movable switch arm 70 of theswitch 29. A recessed portion 71 is formed in the outer peripheral edgeof the cam 67 to cooperate with the follower projection 69 when thecontrol knob 35 is in the full-on" or "Bright position to close switch29. Accordingly, for all positions of knob 35 other than the Brightposition, the switch 29 remains open. The cam 68 cooperates with acam-follower projection 72 formed on the movable switch arm 73 of switch28. A projection 74 is formed on cam 68 and is arranged to engage thefollower projection 72 on the movable switch arm to open switch 28 whenthe control knob 35 is rotated in a counterclockwise direction to reachits OIT position. For all other positions of the control knob, theswitch 28 is closed.

Since the control shaft of the variable resistanceswitch assembly 23actuates both the wiper arm for the potentiometer 60 and the cams 67 and68 of the switch portion simultaneously, it is apparent that a singlecontrol operated by rotation of knob 35 is provided to place the switchin any of its desired positions. Accordingly, the lamp or lamps formingthe load for the dimmer switch of the invention may be turned completelyoff, or on to full brightness, or may be dimmed over a continuouslyvariable range. all by means of a single operating control. By employingthe diode 22, which may be a semiconductor, for example. in the phaseshift circuit for the silicon controlled rectifier, it is possible tomaterially reduce the size of the variable resistance portion 60 of thevariable resistance switch assembly 23, to thereby greatly reduce theoverall physical size of the dimmer switch. As shown in FIG. 7 of thedrawings, this permits a number of dimmer switches to be mounted in asingle, standard size, electric outlet box 80. The three dimmer switches10. constructed in accordance with the teachings of the presentinvention, are supported in the outlet box by means of a mounting strap81 which is secured to the box by screws 82. The strap 81 may be of the"Despard type, or may comprise any other convenient mounting arrangementas known in this art. Each of the dimmer switches 10 is secured to aseparate, interchangeable mounting plate 83, which engages theprojections 55 formed on the housing 54 of each switch and the mountingplates are, in turn, secured to the mounting strap 81.

Suitable circuit values for the dimmer switch shown in FIG. 1 of thedrawings for use with a silicon controlled rectifier, such as a GeneralElectric Co. Type C368, for example, are given by way of illustration asfollows:

Variable resistance 26-l00,000 ohms, approximately /3 watt.

Capacitor 24.5 mt"., volt D.C.

Capacitor 39-.25 mf., 200 volt A.C.

Resistor 36-7500 ohms.

Resistor 38IOO ohms and larger depending upon the gate currentcharacteristic of the particular silicon controlled rectifier employed.

As hcreinbefore explained, while continuous variability is not providedthroughout the entire range from "oIf to "full power," the dimmer switchof the invention is particulnrly effective for controlling incandescentlamps over a range of, for example, 2% to of their rated light output.It may be noted that by the addition of an oppositely polarized diode inparallel with the silicon controlled rectifier l6 and appropriateswitching, the range of power from 50% to 100% could be provided withsubstantially continuous control.

Such an alternative form of circuit with a diode rectifier in parallelis shown in FIG. 8. The circuit of FIG. 8 includes the elements of thecircuit of FIG. 1 and, in addition, a parallel circuit is providedbetween terminals 11 and 12 comprising a diode rectifier 102 polarizedoppositely to the silicon controlled rectifier 16. In series with thediode rectifier 102, is a single-pole, single-throw switch When theswitch 101 is moved to the positioned marked Low to open the circuit,the operation of the continuously variable dimmer switch issubstantially as explained with reference to FIG. I, and gives acontinuously variable range of power between zero and fifty percent offull power. When switch I01 is moved to the position marked High" andthe parallel circuit is completed, it will be noted that one-half of thealternating current wave form will be shunted around the siliconcontrolled rectifier l6, and the minimum controllable power will hefifty percent of the full power. Adjustment of the silicon controlledrectifier circuit will then yield a range of continuously variable powerbetween the values of fifty percent and one hundred percent full power.

Switch 29 and leads 32 and 33 to provide full power in FIG. I willgenerally be unnecessary in the circuit of HG. 8, but may be retainedand will provide the incidental advantage of relieving the load from thediode and silicon controlled rectifier during full power operation.Additionally, it is possible to employ two of the dimmer switches 10 ofthe invention in parallel circuit, but with opposite polarity, to givecontinuous power control above of full power. This arrangement also hasthe added advantage of permitting the controls of the two dimmercircuits to be ganged together to reduce the average current to the loadto zero, so that no substantial direct current component would exist todamage those load devices which are for encrgization by alternatingcurrent only.

Such an alternative form of double dimmer circuit arrangement isillustrated in FIG. 9, wherein the circuitry shown in the enclosure 11of FIG. I is retained and sub stantially duplicated in FIG. 9, exceptthat capacitor 39, leads 40, leads 32 and 33, and switch 29 are notduplicated, as such duplicate elements obviously would be superfluous.

In FIG. 9, elements are given the same reference numerals as in FIG. I,except for the addition of the sutfix a and the sutfix b in the case ofretained and duplicated elements, respectively.

Elements in the FIG. 9 circuit retained from the FIG. 1 circuit operatein the same manner, already explained with reference to FIG. I.Duplicated elements in FIG. 9 also operate in a manner similar to theFIG. I circuit, except that it will be noted that silicon controlledrectifier 16b in FIG. 9 is connected with its associated circuitrybetween terminals 11 and 12 so that it is oppositely olarized withrespect to the silicon controlled rectifier 16a. Thus each of thesilicon controlled rectifiers operates substantially independently onopposite halves of the alternating current wave formation, and the rangeof continuous adjustment in terms of percentage of full power isdoubled.

Usually it will be desirable to gang together the controls, as indicatedby the dashed line in FIG. 6, in order that full-range control may beobtained with a single control. This also substantially eliminates anydirectcurrent component through the load circuit, as previouslyexplained.

It is believed apparent that many changes could be made in the aboveconstruction and many apparently widely different embodiments of thisinvention could be made without departing from the scope thereof. Forexample, other, similar devices could be substituted for the siliconcontrolled rectifier l6, and the half-wave diode 22 could be replaced byother types of rcctifiers. Additionally, other physical forms for thevariable resistanceswitch assembly 23 could be utilized and otherarrangements of the component parts of the switch could be employed ifdesired. Accordingly it is intended that all matter contained in theabove description or shown in the accompanying drawings shall beinterpreted as illustrative and not in a limiting sense.

What is claimed is:

l. A power control and switch device providing sub stantially continuouscontrol of power supplied to a loud over a substantial range of powervalues comprising two terminals for connecting said device in series inone side of the two sides of the power line from an alternating currentpower source supplying current to the load, a rectifier element having acathode, anode and gating electrode, a switch, means connecting saidrectifier element between said terminals to cause said rectifier elementto be con nected by means of its cathode and anode terminals in seriesbetween said two terminals, means connecting said switch between saidtwo terminals to selectively provide a separate electrical path betweensaid two terminals, and a variable time delay means energized from saidtwo terminals for providing a gating signal to the gating electrode ofsaid rectifier element, said gating signal being controllable toinitiate conduction by said rectifier element at instants of timebearing a controllable relation with respect to the beginning ofalternating current cycles of power available at said two terminals,whereby a portion of each alternating current cycle, which portion iscontinuously controllable in duration over a predetermined range, may besupplied to the load connected in circuit with said device.

2. Apparatus as claimed in claim 1 wherein said rectifier element is acontrolled rectifier and further including a further rectifier elementand means for connecting the last said rectifier element in shuntbetween said two terminals with its polarization opposite to that ofsaid controlled rectifier.

3. Apparatus as claimed in claim 1 further including a secondary circuitsubstantailly the duplicate of that of said device of claim 1, saidsecondary circuit being connected in shunt between said two terminalswith its polarization opposite to that of the said rectifier of claim 1.

4. A power control device as claimed in claim I, further comprising ahousing and a member for mounting said rectifier element, said memberbeing formed of a good heat conducting material and extending along atleast a portion of the walls of said housing intcriorly thereof, so thatsaid member acts as a heat sink to dissipate the heat produced by saidrectifier.

[5. A power control device providing substantially continuous control ofpower supplied to a load over a substantial range of power values, comrising two terminals for connecting said device in series circuit in oneside of the two sides of a power line supplying current to the load; acontrol rectifier having the anode and cathode electrodes thereofserially coupled between said terminals, said rectifier being of thetype having a gate electrode in addition to said anode and cathodeelectrodes for controlling the forward conduction thereof; a variabletime delay circuit including a capacitor, said delay circuit having theinput thereof serially coupled between said terminals and the outputthereof coupled to the gate electrode of said controlled rectifier andunidirectional current conducting means connected in series with saidcapacitor to provide a unidirectional current path through saidcapacitor from one to the other of said terminals, whereby said delaycircuit is adapted to control the portion of an alternating currentcycle applied to said terminals over which said rectifier conducts tothereby control the power applied to the load] [6. A power control andswitch device providing sub stantially continuous control of powersupplied to a load over a substantial range of power values comprisingtwo terminals for connecting said device in series in one side of thetwo sides of the power line from an alternating current power sourcesupplying current to the load, a semiconductor control element havingfirst and second electrodes, said control element normally beingsubstantially non-conductive between said first and second electrodesand being adapted to be rendered conductive in at least one direction bya control signal, means connecting said control element in seriesbetween said two terminals by means of its first and second electrodes,and a variable time delay means energized from said two terminals forproviding a control signal to said control element said control signalbeing controllable to initiate conduction by said control element atinstants of time bearing a controllable relation with respect toalternating current cycles of power available at said two terminals,whereby portions of alternating current cycles, which portions arecontinuously controllable in duration over a predetermined range, may besupplied to the load connected in circuit with said device] [7. A powercontrol and switch device providing substantially continuous control ofpower supplied to a load over a substantial range of power valuescomprising two terminals for connecting said device in series in oneside of the two sides of the power line from an alternating currentpower source supplying current to the load, a semiconductor controlelement having first and second electrodes, said control elementnormally being substantially nonconductive between said first and secondelectrodes and being adapted to be rendered conductive in at least onedirection by a control signal, means connecting said control element inseries between said two terminals by means of its first and secondelectrodes, a variable time delay means energized from said twoterminals for providing said control signal to said control element, aswitch and means connecting said switch to selectively open the circuitfor said control signal between one of said terminals and said controlelement, said control signal being controllable by said time delay meansto initiate conduction by said control element at instants of timebearing a controllable relation with respect to alternating currentcycles of power available at said two terminals, whereby portions ofalternating current cycles, which portions are continuously controllablein duration over a predetermined range may be supplied to the loadconnected in circuit with said device] 8. A power control and switchdevice for use as a wiring device to be installed in a buildingproviding substantially continuous control of power supplied 10 a loadover a substantial range of power values, said device comprising aninsulating housing adapted to fit in an outlet box, two terminals forconnecting said device in series in one side of the two sides of thepower line from an alternating current power source supplying current tothe load, said power line comprising conductors of a building wiringcircuit, means for respectively connecting said terminals to conductorscomprising said one side of said power line, a semiconductor controlelement within said housing having first and second electrodes, saidcontrol element normally being substantially non-conductive between saidfirst and second electrodes and being adopted to be rendered conductivein at least one direction by a control signal, means within said housingconnecting said control element in series between said two terminals bymeans of its first and second electrodes, variable time delay meanswithin said housing energized from said two terminals for providing acontrol signal to said control element, within said housing a mechanicalswitch arranged to selccllvely open the circuit for said control signalbetween one 0) said terminals and said control element, and acontinuously variable manually operable control member [or said timedelay means extending outside said housing, said mechanical switch beingmocha/u lcally coupled to said control member and mid time delay meansbeing controllable by operation of said control member to initiateconduction by said control element at instants of time bearing acontrollable relation will! respect to alternating current cycles 0]power available at said two terminals, whereby portions of alternatingcurrent cycles, which portions are continuously controllable in durationover a predetermined range, may be supplied to the load connected incircuit with said device.

9. A power control and switch device for use as a wiring device to beinstalled in a building providing subs/antially continuous control ofpower supplied to a load over a substantial range of power values, saiddevice comprising an insulating housing adapted to fir in an ()Hllt'lbox, two terminals for connecting said device in series in one side ofthe two sides of the power line from an alternating current power sourcesupplying current to the load, said power line comprising conductors ofa building wiring circuit, means for respectively connecting saidterminals to conductors comprising said one side of said power line, asemiconductor control element within said housing having first andsecond electrodes, said control element normally being substantiallynon-conductive between said first and second electrodes and beingadapted to be rendered conductive in at least one direction by a controlsignal, means within said housing connecting said control element inseries between said two terminals by means of its first and secondelectrodes, variable time delay means within said housing energized fromsaid two terminals [or providing a control signal to said controlelement, a mechanical switch within said housing arranged to selectivelyopen the energization circuit [or said time delay means and a manuallyoperable control memher for said time delay means extending outside saidhousing, said switch being mechanically connected to said control memberfor actuation thereby, and said time delay means being controllable byoperation of said control member to initiate conduction by said controlelement at instants of time bearing a controllable relation with respectto alternating current cycles of power available at said two terminals,whereby portions of alternating current cycles, which portions arecontinuously controllable in duration over a predetermined range, may besupplied to the load connected in circuit with said device.

10. A power control and switch device for use as a wiring device to beinstalled in a building providing substantially continuous control ofpower supplied to a load over a substantial range of power values, saiddevice comprising an insulating housing having front, side, and backsections adapted to fit in an outlet box flush with the front thereof,two terminals for connecting said device in series in one side the twosides 0) the power line lrom an alternating current power sourcesupplying current to the load, said power line comprising conductors ofa building wiring circuit, means [or respectively connecting saidterminals to conductors comprising said one side of said power linepresent in said outlet box, a semiconductor control element securedwithin said housing having first and second electrodes, said controlelement normally being substantially non-conductive between said firstand second electrodes and being adapted to be rendered conductive in atleast one direction by a control signal, means within said housingconnecting said control element in series between said two terminals bymeans of its first and second electrodes, a first capacitor directlyconnected between said two terminals, variable time delay meansinclnding a second capacitor and means for varying its charging ratewithin said housing energized front said two terminals for providing acontrol signal to said control element, a mechanical switch arranged toselectively open the circuit for said time delay means between one ofsaid terminals and said control element, and a continuously variablemanually operable control member for said time delay means extendingthrough the front portion of said housing, said mechanical switch beingmechanically coupled to said control member to provide positive cut-oflof current through said time delay means and said control element andsaid time delay means being controllable by operation of said controlmember to selectively initiate conduction by said control element atinstants of time bearing a controllable relation with respect toalternating current cycles of power available at said two terminals,whereby portions of alternating current cycles, which portions arecontinuously controllable in duration over a predetermined range, may besupplied to the load connected in circuit with said device.

References Cited by the Examiner The following references, cited by theExaminer, are of record in the patented file of this patent or theoriginal patent.

UNITED STATES PATENTS 2,001,837 5/1935 Craig 323-22 X 2,896,125 5/1957Morton 3l5272 2,877,359 3/1959 Ross 30788.5 2,920,240 1/1960 Macklcm3l5-201 2,981,866 4/1961 Tsicn 315272 3,061,744 3/1962 Spira 307-1463,032,688 5/1962 Spira 315 272 3,128,440 4/1964 Davis 323- OTHERREFERENCES 1. Notes on the Application of the Silicon ControlledRectifier, Semiconductor Products Department of the General ElectricCompany, December 1958, pp. 41-43.

2. A Survey of Some Circuit Applications of the Silicon ControlledSwitch and Silicon Controlled Rectifier, Applications and Circuit DesignNotes of the Solid State Products, Inc, August 1959. BulletinD420-02-859, p. 27.

JOHN F. COUCH, Primary Examiner.

ORIS L. RADER, Examiner.

K. D. MOORE, J. B. SOTAK, G. P. HAAS,

Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Reissue No. 26,119December 6, 1966 Saul I. Slater It is hereby certified that error appearin the above numbered patent requiring correction and that the saidLetters Patent should read as corrected below.

Column 1, line 34, after "devices" strike out the comma; column 5, line8, for "begin" read begins column 10, line 54, strike out "within saidhousing" and insert the same after "switch" in same line 54, same column10.

Signed and sealed this 5th day of September 1967.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesting Officer Commissioner ofPatents

